Furan has been hydrogenated in a neutral or weakly acid aqueous system in the presence of a nickel catalyst as shown by Russian Pat. No. 114,928 (1958) to P. A. Moshkin et al. to produce 1,4-butanediol, tetrahydrofuran and small amounts of butanol. One example shows the inclusion of a small amount of formic acid in the reaction mixture. James M. Watson, Ind. Eng. Chem. Prod. Res. Develop. 12 (4) 310-311 (1973) shows the same general reaction where acetic acid is present in the reaction mixture. The Watson publication also discloses that the reduction of furan under various conditions using Ni, Pd, Pt and Ru catalysts has generally been reported to give either tetrahydrofuran or 1-butanol or mixtures thereof (Rylander, 1967; Augustine, 1965; Smith & Fuzek, 1949). In both processes, the yield of 1,4-butanediol is not as high as could be desired and unwanted by-products are produced, such as the mono- and diformate, and mono- and diacetate esters of 1,4-butanediol. These esters have boiling points quite close to the boiling point of 1,4-butanediol itself and it is expensive and difficult to distill them off; in fact, the diacetate ester of 1,4-butanediol has the same boiling point as 1,4-butanediol and cannot be separated by distillation. Accordingly, the 1,4-butanediol produced by these processes contains the esters as impurities. Pure, "polymer grade" 1,4-butanediol is necessary in the manufacture of useful high molecular weight polyesters from terephthalic acid. Therefore, the impure diol produced by the above-mentioned prior art processes cannot be used directly.
A welcome contribution to the art would be a process that produces 1,4-butanediol in good yields, without substantial impurities which cannot be easily separated from the highly desired 1,4-butanediol.